[v4 1/4] arm64: kvm: add a cpu tear-down function

AKASHI Takahiro
2015-05-08T01:18:57Z

Cpu must be put back into its initial state, at least, in the
following cases in order to shutdown the system and/or re-initialize cpus
later on:
1) kexec/kdump
2) cpu hotplug (offline)
3) removing kvm as a module

To address those issues in later patches, this patch adds a tear-down
function, kvm_cpu_reset(), that disables D-cache & MMU and restore a vector
table to the initial stub at EL2.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
---
arch/arm/kvm/arm.c | 15 +++++++++++++++
arch/arm/kvm/mmu.c | 5 +++++
arch/arm64/include/asm/kvm_asm.h | 1 +
arch/arm64/include/asm/kvm_host.h | 11 +++++++++++
arch/arm64/include/asm/kvm_mmu.h | 7 +++++++
arch/arm64/include/asm/virt.h | 11 +++++++++++
arch/arm64/kvm/hyp-init.S | 32 ++++++++++++++++++++++++++++++++
arch/arm64/kvm/hyp.S | 16 +++++++++++++---
8 files changed, 95 insertions(+), 3 deletions(-)

diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 07e7eb1..251ab9e 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -897,6 +897,21 @@ static void cpu_init_hyp_mode(void *dummy)
__cpu_init_hyp_mode(boot_pgd_ptr, pgd_ptr, hyp_stack_ptr, vector_ptr);
}

+static void kvm_cpu_reset(void *dummy)
+{
+ phys_addr_t boot_pgd_ptr;
+ phys_addr_t phys_idmap_start;
+
+ if (__hyp_get_vectors() == hyp_default_vectors)
+ return;
+
+ boot_pgd_ptr = kvm_mmu_get_boot_httbr();
+ phys_idmap_start = kvm_get_idmap_start();
+ __cpu_reset_hyp_mode(boot_pgd_ptr, phys_idmap_start,
+ hyp_default_vectors,
+ kvm_virt_to_trampoline(__kvm_hyp_reset));
+}
+
static int hyp_init_cpu_notify(struct notifier_block *self,
unsigned long action, void *cpu)
{
diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 3e6859b..3631a37 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -1490,6 +1490,11 @@ phys_addr_t kvm_get_idmap_vector(void)
return hyp_idmap_vector;
}

+phys_addr_t kvm_get_idmap_start(void)
+{
+ return hyp_idmap_start;
+}
+
int kvm_mmu_init(void)
{
int err;
diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index 4f7310f..f1c16e2 100644
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -118,6 +118,7 @@ struct kvm_vcpu;

extern char __kvm_hyp_init[];
extern char __kvm_hyp_init_end[];
+extern char __kvm_hyp_reset[];

extern char __kvm_hyp_vector[];

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 8ac3c70..6a8da9c 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -199,6 +199,8 @@ struct kvm_vcpu *kvm_arm_get_running_vcpu(void);
struct kvm_vcpu * __percpu *kvm_get_running_vcpus(void);

u64 kvm_call_hyp(void *hypfn, ...);
+void kvm_call_reset(phys_addr_t boot_pgd_ptr, phys_addr_t phys_idmap_start,
+ unsigned long stub_vector_ptr, unsigned long reset_func);
void force_vm_exit(const cpumask_t *mask);
void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot);

@@ -223,6 +225,15 @@ static inline void __cpu_init_hyp_mode(phys_addr_t boot_pgd_ptr,
hyp_stack_ptr, vector_ptr);
}

+static inline void __cpu_reset_hyp_mode(phys_addr_t boot_pgd_ptr,
+ phys_addr_t phys_idmap_start,
+ unsigned long stub_vector_ptr,
+ unsigned long reset_func)
+{
+ kvm_call_reset(boot_pgd_ptr, phys_idmap_start, stub_vector_ptr,
+ reset_func);
+}
+
struct vgic_sr_vectors {
void *save_vgic;
void *restore_vgic;
diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index 6458b53..facfd6d 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -96,6 +96,7 @@ void kvm_mmu_free_memory_caches(struct kvm_vcpu *vcpu);
phys_addr_t kvm_mmu_get_httbr(void);
phys_addr_t kvm_mmu_get_boot_httbr(void);
phys_addr_t kvm_get_idmap_vector(void);
+phys_addr_t kvm_get_idmap_start(void);
int kvm_mmu_init(void);
void kvm_clear_hyp_idmap(void);

@@ -305,5 +306,11 @@ static inline void __kvm_flush_dcache_pud(pud_t pud)
void kvm_set_way_flush(struct kvm_vcpu *vcpu);
void kvm_toggle_cache(struct kvm_vcpu *vcpu, bool was_enabled);

+extern char __hyp_idmap_text_start[];
+#define kvm_virt_to_trampoline(x) \
+ (TRAMPOLINE_VA \
+ + ((unsigned long)(x) \
+ - ((unsigned long)__hyp_idmap_text_start & PAGE_MASK)))
+
#endif /* __ASSEMBLY__ */
#endif /* __ARM64_KVM_MMU_H__ */
diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h
index 3070096..7fcd087 100644
--- a/arch/arm64/include/asm/virt.h
+++ b/arch/arm64/include/asm/virt.h
@@ -61,6 +61,17 @@
#define BOOT_CPU_MODE_EL1 (0xe11)
#define BOOT_CPU_MODE_EL2 (0xe12)

+/*
+ * HVC_RESET - Reset cpu in EL2 to initial state.
+ *
+ * @x0: entry address in trampoline code in va
+ * @x1: identical mapping page table in pa
+ * @x2: start address of identical mapping in pa
+ * @x3: initial stub vector in pa
+ */
+
+#define HVC_RESET 5
+
#ifndef __ASSEMBLY__

/*
diff --git a/arch/arm64/kvm/hyp-init.S b/arch/arm64/kvm/hyp-init.S
index c319116..2614cfc 100644
--- a/arch/arm64/kvm/hyp-init.S
+++ b/arch/arm64/kvm/hyp-init.S
@@ -115,6 +115,38 @@ target: /* We're now in the trampoline code, switch page tables */
eret
ENDPROC(__kvm_hyp_init)

+ /*
+ * x0: HYP boot pgd
+ * x1: HYP phys_idmap_start
+ * x2: HYP stub vectors
+ */
+ENTRY(__kvm_hyp_reset)
+ /* We're in trampoline code in VA, switch back to boot page tables */
+ msr ttbr0_el2, x0
+ isb
+
+ /* Invalidate the old TLBs */
+ tlbi alle2
+ dsb sy
+
+ /* Branch into PA space */
+ adr x0, 1f
+ bfi x1, x0, #0, #PAGE_SHIFT
+ br x1
+
+ /* We're now in idmap, disable MMU */
+1: mrs x0, sctlr_el2
+ ldr x1, =SCTLR_EL2_FLAGS
+ bic x0, x0, x1 // Clear SCTL_M and etc
+ msr sctlr_el2, x0
+ isb
+
+ /* Install stub vectors */
+ msr vbar_el2, x2
+
+ eret
+ENDPROC(__kvm_hyp_reset)
+
.ltorg

.popsection
diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
index fd085ec..7c3bdee 100644
--- a/arch/arm64/kvm/hyp.S
+++ b/arch/arm64/kvm/hyp.S
@@ -1136,6 +1136,11 @@ ENTRY(kvm_call_hyp)
ret
ENDPROC(kvm_call_hyp)

+ENTRY(kvm_call_reset)
+ hvc #HVC_RESET
+ ret
+ENDPROC(kvm_call_reset)
+
.macro invalid_vector label, target
.align 2
\label:
@@ -1179,10 +1184,14 @@ el1_sync: // Guest trapped into EL2
cmp x18, #HVC_GET_VECTORS
b.ne 1f
mrs x0, vbar_el2
- b 2f
+ b 3f

-1: /* Default to HVC_CALL_HYP. */
+ /* jump into trampoline code */
+1: cmp x18, #HVC_RESET
+ b.ne 2f
+ br x3 // no return

+2: /* Default to HVC_CALL_HYP. */
push lr, xzr

/*
@@ -1196,7 +1205,8 @@ el1_sync: // Guest trapped into EL2
blr lr

pop lr, xzr
-2: eret
+
+3: eret

el1_trap:
/*
--
1.7.9.5